1. Technical Field
The present disclosure relates to a controller for an internal combustion engine and a control method therefor.
2. Description of Related Art
It has been known, for a purpose of injection into cylinders, that high-pressure fuel is supplied to an internal combustion engine of an in-cylinder injection type. The internal combustion engine of this type includes: a high-pressure pump that pressurizes fuel drawn from a fuel tank by a feed pump; and a high-pressure fuel pipe that stores the pressurized fuel. In this internal combustion engine of the in-cylinder injection type, the fuel is supplied from the high-pressure fuel pipe to a high-pressure fuel injection valve for in-cylinder injection.
When a fuel temperature in the high-pressure pump is raised to the boiling point of the fuel or higher, the fuel in the pump may be vaporized. Once the fuel in the pump is vaporized, the high-pressure pump is brought into a so-called vapor lock state. The vapor lock state refers to a state where, even when a pressurizing operation of the high-pressure pump is performed, vapor inside the high-pressure pump is merely compressed, and pressure is not applied to the liquid fuel. In Published Japanese Translation of PCT application No. 2003-513193 (JP 2003-513193 A), a controller for an internal combustion engine that prevents vapor lock is disclosed. The controller for the internal combustion engine in JP 2003-513193 A increases pressure of fuel that is supplied from feed pump to high-pressure pump when the fuel temperature in the high-pressure pump becomes at least equal to a threshold.